Variable pitch propeller



J. M. SHOEMAKER VARIABLE PITCH PHOPELLER July 6, 1937.

Filed Feb. 29, 1932 2 Sheets- Sheet 1 II II III Jmxmtoo dttwm July 6, 1937.

4 J. M. SHOEMAKER VARIABLE PITCH PROPELLER 2 Sheets-Shee t' 2 Filed Feb. 29, 1932 Patented July 6, 1937 UNITED STATES PATENT OFFICE VARIABLE rrron PROPELLER James M. Shoemaker, San Diego, Calif. Application February 29, 1932, Serial No. 595,837

5Claims.

This invention relates to propellers and more particularly to propellers of the type provided with mechanism for varying the pitch of the blades.

to provide a novel variable pitch propeller.

Another object of the invention is to provide,

discontinuance of the pitch varying apparatus atthe will of the operator.

A further object is to provide in a variable pitch propeller of the automatic type, a novel arrangemgent of parts permitting the blades to be locked in position at the will of the operator, thus enabling the propeller to be operated efficiently 25 during low engine throttle conditions.

A still further object is to provide a novel and compact arrangement of parts which shallnot only be light in weight but also capable of efficient and positive operation, which features are 3 especially desirable in instances of installations I on aircraft.

Other objects and novel features of the invention will appear more fully hereinafter from the following detailed description when taken in conection with the accompanying'drawings whereup there is illustrated one form of the invention. It is to be expressly understood, however, that the drawings are for purposes of illustration only and are not designed as a definition of the limits of the invention, reference being had for this purpose to the appended claims.

In the drawings wherein similar reference characters refer to similar parts throughout the several views: V Fig. 1 is a vertical section of a propeller embodying the present invention; a

Fig. 2 is a diagrammatic view partly in section of a portion of the mechanism for varying the pitch. of the propeller blades; and

Fig. 3 is a perspective view of certain parts illustrated in Fig. 1. l

Referring more particularly to Fig. l, a propeller constructed in accordance with the present invention is illustrated therein as being con- 55 stituted by. a hollow engine-driven shaft 4 rotat- One of the objects of the present invention is ably mounted with respect to the engine crank case, a portion of which is indicated at 5, by means of ball bearings 6, and carrying at its outer end portion, a propeller hub 1 formed with a plurality of radially-extending sockets 8 for receiving the root ends of propeller blades 9. Each of these blades is rotatably mounted in its respective socket as by means of a journal bearing Ill and a ball thrust bearing H, and means are provided for automatically rotating the said blades in their sockets to vary the pitch thereof during operation, which means will be referred to more specifically hereinafter.

Preferably, the means for varying the pitch of the propeller blades during rotation of the propeller is automatic in operation and is controlled by a device responsive to the speed of the engine shaft. By this construction, the propeller will serve to effect a governing action upon the engine in order to control therate of revolutions thereof when operated under full-throttle conditions. As shown, such means is constituted by -an hydraulic mechanism having an enginedriven pump l2 and a motor I3' adapted; to be controlled in its operation by means of the pump l2 and being drlvably connected-to each propeller blade for varying the pitch of the latter. Inasmuch as the pump l2 and the motor l3 are of the same form as the Waterbury. transmission 7 and therefore are well known in the art, a detailed description thereof is not thought to be necessary. Moreover, since the elements constituting both of these devices are substantially identical, one only will be briefly described.

As shown diagrammatically in Fig. 2, the pump I2 is constituted by a fluid filled casing l4 having rotatably mounted therein a driving shaft IS. A.

'- plurality of longitudinally-extending pistons I arranged concentrically with respect to the shaft l5 and cooperating with a rotatable cylinder plate I8, are adapted to be rotated by said shaft 1 through a thrust plate l9 to which said pistons are pivotally connected. Cooperating with the cylinder plate I8 and within the casing is a nonrotatable valve plate 20 having a pair of arcuate 4 ports 2| and 22 therein, Fig. v1, which serve alternately as intake and exhaust ports depending upon the direction of flow of the fluid. Suitable pipes or conduits 23 and 24 communicate withthe ports 2| and 22 and serve to conduct the. fluid from the pump l2 to the motor l3. A tilting .box It is pivotally mounted in the casing, in any suitable manner, and when in the position shown in Fig. 2, imparts no throwfto the pistons l1. When the parts are in this position, itwill be understood that no fluid is transmitted from the pump to the motor notwithstanding the fact that shaft I5 is constantly rotating. When, however, the tilting box is'tilted in one direction or the other, the pistons I! will cooperate with the cylinder plate Hi to pump fluid through one of the conduits 23 or 24 to the motor l3, the tilting box l6 of which will be rotated by means of the cylinder plate l8 and pistons H, the fluid being 'returned to the pump by the other conduit. If, how-- ever, the tilting box of the pump be tilted in the reverse direction, fluid will be pumped to the motor in a reverse direction and the direction of rotation of the tilting box therein will be consequently reversed.

Preferably, the motor I3 is housed 'within the rotating hollow shaft 4, and since the pump I2 is stationarily mounted on the casing 5, means are provided for interconnecting the conduits 22 and 23 common to each. As shown, such means comprise a stationary ring 25, Fig. 3, which may be split for ease in assembly; the said ring being provided with a pair of annular grooves 29 and 21, the first-named groove communicating with a duct 28 while the groove 21 communicates with'a duct 29, both of said ducts being formed in the propeller hub 1. Each of the ducts 28 and 29 communicates respectively through conduits 30 and 3| with arcuate openings 32 and 33 formed in the valve plate 20 of the motor l3, such openings being preferably provided with suitable covers in order to prevent leakage of fluid.

In order to transmit movement from the motor l3 to each of the propeller blades to vary the pitch of the latter, when fluid under pressure is conducted from the pump to said motor, the latter is provided with a shaft 34, drivably connected with the rotatable tilting box It and suitably rotatably mounted in the casing of the motor, the said shaft carrying upon its outer end .a bevel pinion 35 adapted to mesh with a corresponding bevel pinion 36. secured upon a shaft 31 extending perpendicularly to the axis of shaft 34. The shaft 31, adjacent its outer extremities, is, suitably journaled in brackets 38 secured to the hub, and the extreme ends of the shaft carry bevel pinions 39 meshing with corresponding bevel pinions 40. These last-named pinions are secured upon worm shafts 41 carrying self-locking worms 4 I which are in constant meshing engagement with the teeth of worm gears 42 secured to the root ends of each blade exteriorly of the hub sockets, see Fig. 1. From the above construction, it will be readily apparent that upon rotation of shaft 34 and consequent rotation of shaft 31, the blades will be rotated in their respective sockets to-either increase or decrease the pitch thereof simultaneously,dependent upon the direction of rotation of shaft 34.

In order to drivably connect the pump l2 and the' engine shaft 4, the latter is adapted to drive a concentric gear 43, Fig. 3, which is adapted to mesh with a gear 44 mounted upon a suitably joumaled lay shaft 45 to which shaft a worm wheel 46 is secured. The shaft l5, suitably rotatably mounted in a stationary portion of the engine casing, carries a bevel pinion 4'I meshing with a corresponding bevel pinion 48-on a shaft operation with worm wheel 46.

49,'the other end of said shaft having secured thereon, a suitable reversible worm 50 for co- ,As heretofore stated, the angularity of the tilting box ii of the fluid motor I 2 willdeter- ,mine the throw of the pistons l1 and hence the degree of pressure of the fluid transmitted to the of which is at all times a measure of the engine speed, and this collar is operatively connected to the tilting box I6 by means of a lever 53, having a stationary pivot 54, and link 55. Preferably an adjustment nut 5| is provided in order to adjust the initial position of the tilting box IE for the purpose of maintaining the latter in a substantially vertical inoperative position at the desired engine speed.

Inasmuch as the above described construction would cause operation of the pump at all times during rotation of the engine shaft, it may be desirable in certain instances, as for example, when it is desired to land an aeroplane equipped with the present invention, or to maneuvcr'at low-throttle conditions, to render the pitch-varying mechanism inoperative, and preferably such action should be under the control of the pilot.

For this purpose, Fig. 3, a by-pass valve 56 is associated with conduits 23, 24 and 51 and 58 conducting fluid from the pump l2 to the motor l3, and such valve is arranged to be manually operated by a connection 59 positioned in such a manner as to be readily accessible to the pilot to effect a disconnection between conduits 23 and 51, and establish communication between conduits 23 and 24, thus interrupting the continuous flow of fluid between the pump and motor and When installing the above-described structure, the position of the weights of the governing mech anism is so adjusted by means of the adjusting nut 5| that the said mechanism will maintain the tilting box in a substantially vertical position, as viewed in Figs. 1 and 2 at the engine speed it is desired to maintain. Under these conditions, if the engine speed does not exceed or fall below this value, the pitch-changing mechanism will be inoperative. However, in the event the engine speed exceeds the predetermined value the governing mechanism will actuate the tilting box HS in such a direction as to cause a flow of fluid from the pump l2 to the motor l3 to cause rotation of shaft 34 and consequent rotation of shaft 31, gears 39 and 40 and worm wheel 42 to effect an increase in the pitch of the blades. This increase in pitch will effect a reduction in the speed of the engine, due to the increased load offered by the propeller, which will in turn affect in the operation of aeroplanes equipped with the present invention, it is highly desirable to land with the pitch of the propeller fixed at a predetermined value. This is accomplished by the present invention by operation of the manually-operated connection .59 prior to landing, whereupon the pitch of the blades will remain fixed even though the engine be operating at less than full throttle. when cruising at fullthrottle, it is desirable to vary the pitch of the blades automatically whereupon it is merely necessary to release the control member 59 whereupon the pitch of the blades will be automatically varied in a manner set forth above. It will also be readily observed that during take-off, the pitch of the blades will be automatically varied by the governing mechanismfrom a low value to a higher value due to increase in air speed and the tendency of the speed of the engine to increase.

There has thus been provided by the present invention a novel automatic variable pitch propeller mechanism so constructed and arranged as to be readily manually controlled to render the automatic feature inoperative. At such tinge the blades will automatically remain in position due to the employment of the self-locking membersin the pitch-varying transmission, it being thus possible to easily and readily dispense with the automatic operation of the pitch-varying mechanism, a feature especially desirable when operating an aeroplane under conditions other than full-throttle. The device herein provided therefore enables maximum propeller and engine efficiency to be obtained during full-throttle operation, when the governing mechanism-is in operation, as well as during part throttle open condi- I tions, represented by discontinuance of the-operation of governing mechanism and consequent functioning of the propeller with a fixed pitch.

While there has been shown and described one embodiment of the invention only, it is to be understood that the same is not limited thereto but may be embodied in various forms. Referencewill therefore be had to the appended claims for a definition of the limits of the invention.

What is claimed is:

1. In combination with a rotatable shaft having a propeller hub drivably connected thereto, a plurality of blades rotatably mounted in said hub, self-locking mechanism operable to rotate the blades in the hub to vary their pitch, hydraulic means for operating said mechanism to positively increase and decrease the pitch of the blades, said means including a pump and a motor, said motor being rotatable with said shaft, centrifugally operate mechanism for controlling said pump, conduits for interconnecting said pump andmotor, and a manually controlled by-pass valve located in one of said conduits for by-passing fluid from the outlet of the pump to the inlet thereof whereby the motor will be rendered inoperative and the pitch. of the blades will remain fixed in the last adjusted position.

2.. In combination with a rotatable shaft having a propeller hub, a plurality of blades rotatably carried by said hub, transmission mechanism including self-locking members'operable to rotate the blades in the hub to vary their pitch, hydraulic means for operating said mechanism to positively increase and decrease the pitch, said means including a pump and a motor, said motor being" rotatable with said shaft, centrifugally-operated means for governing the action of said. pump, conduits for interconnecting said pump and motor, and a manually controlled by-pass valve located in one of said conduits for rendering said motor inoperative at will whereby the pitch of the blades will remain fixed in the last adjusted position.

3. In combination with a rotatable shaft having a propeller hub, a plurality of blades rotatably 1 mounted in said hub, mechanism including selflocking members operable to rotate the blades in the hub to vary the pitch, hydraulic means including a pump and a motor for operating said mechanism to positively increase and decrease, the

control of the operation thereof, centrifugallyoperated means responsive to the speed of said shaft for controlling said tiltable member, and

means for rendering said pump inoperative to affect the motor at the will of the operator whereby the pitch of the blades will remain fixed i the last adjusted position. v 4. In a variable pitch propeller having a rotatable shaft, a hub drivably connected with said shaft, a plurality of propeller blades rotatably mounted in said hub, self-locking mechanism -20 pitch, said pump having a tiltable member for cooperating with each blade, a fluid-operated mo.-

tor carried by said shaft and interconnected with said mechanism, a pump for supplying fluid 'un-' der pressure to said motor to operate the latter to positively increase and decrease the pitch of said blades through said mechanism, means responsive to the speed of rotation of the shaft for controlling the pump, and means for rendering said pump motor disposed within said hollow shaft and ro-- tatable therewith for positively increasing and decreasing the pitch of said blades, transmission mechanism interconnecting said motor and the blades, said mechanism including self-locking members, a relatively stationarily mounted pump for supplying fluid under pressure to said motor,

said pump having an inlet and an outlet, centrifugally-operated means responsive to the-rotative speed of said shaftfor controlling the operation .of-said pump in order to vary the outputth'ereof,

and manually operable means for by-passing the fluid from the inlet to the outlet of the pump for effecting a discontinuance in the operation of the motor, said self-locking members maintaining the pitch of the blades fixed- JAMES M. SHOEMAKER. 

